Light-duty liquid (LDL) or gel detergent compositions useful for manual dishwashing are well known in the art. Such products are generally formulated to provide a number of widely diverse performance and aesthetics properties and characteristics. First and foremost, liquid or gel dishwashing products must be formulated with types and amounts of surfactants and other cleaning adjuvants that will provide acceptable solubilization and removal of food soils, especially greasy soils, from dishware being cleaned with, or in aqueous solutions formed from, such products.
Heavily soiled dishware can present special problems during manual dishwashing operations. Articles such as plates, utensils, pots, pans, crockery and the like may be heavily soiled in the sense that relatively large amounts of food soils and residues may still be found on the dishware at the time such soiled dishware is to be manually washed. Dishware may also be heavily soiled in the sense that food soil residues are especially tenaciously adhered or stuck to the surfaces of the dishware to be cleaned. This can result from the type of food soils present or from the nature of the dishware surfaces involved. Tenacious food soil residues may also result from the type of cooking operations to which the soiled dishware had been subjected. To clean such dishware an appropriate surfactant combination must be employed.
In addition to being suitable for cleaning dishware, LDL or gel compositions will also desirably possess other attributes that enhance the aesthetics or consumer perception of the effectiveness of the manual dishwashing operation. Thus, useful hand dishwashing liquids or gels should also employ materials that enhance the sudsing characteristics of the wash solutions formed from such products. Sudsing performance entails both the production of a suitable amount of suds in the wash water initially, as well as the formation of suds which last well into the dishwashing process.
Hand dishwashing liquids or gels should also employ materials that enhance product phase stability at low temperatures. Lack of phase stability can lead to unacceptable theological and aesthetic properties as well as to performance issues. Such low temperatures can be encountered in warehouses, in the consumer's garage, in the consumer's automobile, during street vending, on the kitchen window sill, and the like. Further, hand dishwashing liquids and gels should employ materials that enhance the dissolution, or rate of product mixing, with water. Further, hand dishwashing liquids and gels should employ materials that enhance the tolerance of the system to hardness, especially to avoid the precipitation of the calcium salts of anionic surfactants. Precipitation of the calcium salts of anionic surfactants is known to cause suppression of suds and irritation to the skin.
Given the foregoing, there is a continuing need to formulate manual dishwashing liquids and gels that provide an acceptable and desirable balance between cleaning performance and product aesthetics. Accordingly, it is an object of the present invention to provide light-duty liquid or gel dishwashing compositions which are especially effective at removing food soils from dirty dishware when such compositions are used in the context of a manual dishwashing operation.
It has further been found, that the mid-chain branched surfactants provide significantly improved tolerance to hardness, significantly improved low temperature stability of the finished product and significantly improved rates of mixing of the product with water.
It is a further object of this invention to provide such compositions having desirable rheological characteristics for use in either a direct application to dishware context or in an aqueous dishwashing solution context.
It is a further object of the present invention to realize such compositions that provide suitable and desirable sudsing performance.
It has been found that certain selected surfactant systems which comprise the mid-chain branched surfactants defined below, suds boosters, viscosity control agents and other adjuvants can be made to provide dishwashing compositions that achieve the foregoing objectives. The elements of these selected combinations of ingredients are described as follows: